Process of preparing acid phosphate



sul

Patented May 26, 1925.

um'ro ATET oFFica. I

WILLIAE E. STOKES, OF ROCKVILLE CENTER, NEW YORK, ASSIGNOR TO ROYAL BAK- ING POWDER COMPANY, OF NEW YORK, N. Y..

n'oon'rona'rron or NEW. mnsnr.

PROCESS OF PREPARING ACID IEHOSPHA'J! 11".

Io Drawing.

To all whom it may concern:

Be it known that I, WILLIAM E. S'roxns, a citizen of the United States, residing in Rockville Center, Nassau County, in the State of New York, have invented new and useful Improvements in Processes of Preparing Acid Phosphate, of which the following is a specification.

The invention relates to a process for pre- 0 paring acid phosphate, and has for its principal objects the production of exceptionally pure monobasic phosphate at comparatively small cost. Monocalcium phosphate, for instance, produced by 15 a considerable percentage of dicalciumphosphate and a small percentage of free phosphoric acid. It has been found impracticable to eliminate the free phosphoric acid without materially reducing the aci strength. by reaction between the neutralizing agent orv agents and a portion of the I mo'nocalcium hosphate, forming dicalcium phosphate. object of the invention is the production of monocalcium phosphate substantiallyfree from dicalcium phosphate or free phosphoric acid, or containing amounts thereo so small as not materially to aflect the stability or acid strength of the phosphate. I I have discovered that by drying a solution of monocalciumvphosphate in which there is sufiicient free phosphoric acid to keep .the dicalcium phosphate from being precipitated and then mixing" with this substantially dry product, finely divided calneutralizing agent,

cium carbonate or other .an exceptionally pure monocalcium phosphate is obtained. I prefer to use calcium carbonate as the neutralizing agent, because 40 its reaction with phosphoric acid does'not occasion the difficulties resulting from endothermic reactions. I havefound that the addition of the neutralizing agent in substantially dry form to the substantiall dry' powder produces a better product, an also makes available rocesses wherein the solu tion of monocalclum phosphate is drled and purified without the difliculties and expenses with (as, for instance, the common treatment huric acid). involved in present practice, thus decreases the. cost of manufacture.

usual .-methods contains Application filed January 24, 1923. Serial No. 514,679.

of the invention, a solu tlon of monocalcium phos hate containing some free phosphoric aci dried, preferably by spray or vacuum drymg, at. proper temperature. If the solut on has been made, as is common, by partially neutralizing a solution of phosphoric acid with some calciumsalt, followed by filtermg, it may contain approximately six per cent, more or less, of free acid; To the product resulting from substantially drying this solution, is added sufiicient substantially dry neutralizing agent, preferably somewhat more than half as much calcium carbonate as there is free acid present. It is desirable to add more than the amount theoretically necessary to neutralize the free acid, because the excess is of value in stabilwing and preventin dissociation of the phosphate molecule. he result is a monocalcium phosphate of higher strength than those commonly used, free from free phosphoric acid. Calcium phosphate is mentioned, but it will be understood that the application of the invention to ammonium, magnesium and other phosphates, is contemplated. I have found that this dry neutralization is not only efiective, but avoids the difliculties connected with efiorts to neutral- 1ze freephosphoric' acid in acid phosphate solutions of varying moisture content.

I claim In the practice 1. A process for pre arm'g monobasi-c phosphate comprising de ydrating a solution of monobasic phosphate containing some free phosphoric acid and mixin with the substantially dry product thereo substantially dry calcium carbonate. it

2. process for preparing monobasic phosphate comprising dehydrating a solution of monobasic" phosphate containing some free phosphoric the substantially dry roduct stantially dry neutra 3. A method of stabilizing acid phosphate comprising addin calcium carbonate to substantially dry aci phosphate.

thereof, a subizmg agent.

STOKES. v

is substantially acid and mixing-with 

